Microwave diode tuning circuit

Abstract

A microwave diode tuning circuit including am IMPATT diode holder of coaxial form and an adjustable capacitor connected in a parallel resonant circuit by microstrip transmission line. The tuning circuit includes a stabilization network and a bias insertion network. Optionally, the tuning circuit may include a hybrid junction for coupling two such diode tuning circuits together. the diode holder includes an internally-externally threaded sleeve providing means for continuously adjusting, through a limited range, the inductance of the resonant circuit.

The invention claimed is: 
     
       1. A tuner for combining a microwave diode, a variable inductor and a variable capacitor into a resonant circuit, the impedance of which is matched to the impedance of a microwave transmission line, comprising a microstrip transmission line including an insulating substrate, a conductive circuit track on one surface of said substrate and a ground plane on the surface of said substrate opposite said one surface thereof;   a microwave diode holder of coaxial form including an outer conductor, a center conductor and a sleeve extending partially over the length of said center conductor and supporting said center conductor axially within said outer conductor, said outer conductor being conductively connected to said ground plane,   said sleeve being conductively connected to said center conductor and said outer conductor and being longitudinally adjustable along the length of said center conductor;   a microwave diode having anode and cathode electrodes, one of said electrodes being conductively connected to that end of said center conductor within said outer conductor and extending beyond said sleeve;   impedance matching means having an impedance value intermediate between the impedance value of said diode and the characteristic impedance value of said circuit track for conductively connecting the other electrode of said diode to said circuit track; and   an adjustable capacitor connected between said ground plane and said circuit track at a point on said circuit track beyond said impedance matching means.   
     
     
       2. A tuner as claimed in claim 1 wherein said ground plane of said transmission line comprises: a conductive housing coextensive with said insulating substrate of said transmission line, said insulating substrate being secured to one surface of said housing.   
     
     
       3. A tuner as claimed in claim 2 wherein said microwave diode holder extends perpendicularly to said one surface of said housing. 
     
     
       4. A tuner as claimed in claim 2 wherein said adjustable capacitor comprises: means providing a conductive path from said point on said circuit track through said transmission line substrate to a point on said opposite surface of said substrate opposite said point on said conductive track;   an aperture in said housing defining a clearance area surrounding said point on said opposite surface of said substrate; and   a conductor extending into said aperture and in electrical contact with said housing, said conductor being adjustable axially within said aperture to vary the distance between said conductor and said point on said opposite surface of said substrate.   
     
     
       5. A tuner for combining a microwave diode, a variable inductor and a capacitor into a resonant circuit, the impedance of which is matched to the characteristic impedance of a microwave transmission line, comprising: a microstrip transmission line including a planar insulating substrate and a linear conductive circuit track on one surface of said substrate;   a conductive housing having one surface thereof coextensive with said substrate, said substrate being supported by said housing with the surface of said substrate opposite said one surface thereof being adjacent to said one surface of said housing;   a second threaded aperture extending through said housing concentrically with said first aperture of said substrate;   an impedance transformer seated in said second aperture, said transformer being insulated from electrical contact with the wall of said second aperture, a portion of said transformer extending through said first aperture and electrically contacting said one end of said circuit track;   an internally-externally threaded conductive sleeve threaded into said aperture above said impedance transformer;   a first threaded conductive rod threaded through said sleeve and extending into said said second aperture;   a microwave diode mounted on the end of said first rod extending into said second aperture with one electrode of said diode in electrical contact with said first rod and with the other electrode of said diode in contact with said transformer whereby the portion of said first rod extending beyond said sleeve into said second aperture constitutes an inductor connected in series with said diode, the inductance of which is variable in accordance with the depth to which said sleeve is threaded into said second aperture; and   a capacitor for resonating with said inductor, said capacitor being connected to a first point on said circuit track at a first location beyond said one end of said circuit track.   
     
     
       6. A tuner as claimed in claim 5 wherein said capacitor is variable. 
     
     
       7. A tuner as claimed in claim 6 wherein said capacitor comprises: a conductor extending through said substrate to a second point on said substrate opposite said first point on said circuit track;   a third, threaded aperture in said housing, said third aperture being concentric with said second point and providing a clearance area in said housing surrounding said second point; and   a second, threaded rod threaded into said third aperture, said second rod being in electrical contact with the wall of said third aperture, the end of said second rod within said third aperture being spaced from said second point,   whereby the capacitance of said capacitor is adjustable in accordance with the depth to which said second rod is threaded into said third aperture.   
     
     
       8. A tuner as claimed in claim 5, with additionally: a third point on said circuit track at second location on said circuit track beyond said first location thereon;   means for applying a d.c. bias to said third point; and   means for blocking the flow of bias current through the end of said circuit track opposite said one end thereof.   
     
     
       9. A tuner as claimed in claim 5, with additionally: a first stub of circuit track having one end thereof connected to said first point on said circuit track and the opposite end thereof open circuited, said first stub having a length equal to one half the operating wave length of said microwave diode.   
     
     
       10. A tuner as claimed in claim 9, with additionally: a resistor having a resistance equal to the characteristic impedance of said circuit track, said resistor being connected in series with said first stub.   
     
     
       11. A tuner as claimed in claim 9, with additionally: a third point on said circuit track at a second location on said circuit track beyond said first location thereon;   means for blocking the flow of bias current through the end of said circuit track opposite said one end thereof.   
     
     
       12. A tuner as claimed in claim 11, with additionally: a second stub of circuit track having one end thereof connected to said third point on said circuit track and the opposite end thereof open circuited, said second stub having a length equal to one-half the operating wave length of said microwave diode.   
     
     
       13. A tuner as claimed in claim 12, with additionally: a third stub of circuit track;   a fourth stub of circuit track;   said third and fourth stubs each having a length equal to one-fourth of the operating wave length of said microwave diode;   said fourth stub having one end thereof connected to one end of said third stub and the other end of said fourth stub open circuited;   said third stub having said one end thereof connected to said fourth stub also connected to said means for applying bias and the other end of said third stub connected to said third point on said circuit track